抄録
In recent years, a requirement has emerged for cost-effective techniques for the detection of leaks of methane gas, the principle ingredient of natural gas. To realize such techniques, laser absorption spectroscopy at the absorption line of methane has been intensively researched. The author has developed two types of equipment for methane gas leak detection using a compact and low-cost near-infrared diode laser (InGaAsP DFB laser,λ=1.65372μm). One system can survey the leaks in underground gas pipes while driving along the roadabove the pipes. The other can provide remote detection and pinpointing of the leaks in exposed gas pipes. To accomplish highly sensitive detection, despite weak absorption in near-infrared range, these two equipments employ second-harmonic detection of wavelength modulation spectroscopy.
